Rotary spading machine



Nov. 9, 1965 A. HOROWITZ ROTARY SPADING MACHINE '7 Sheets-Sheet 1 FiledAug. 5, 1963 a confac/ c/rc/e b=9enerafing0hcle c mva/uie c/rc/eINVENTOR ALEXANDRE HOROW/TZ ATToRNEYs Nov. 9, 1965 A. HOROWlTZ 3,216,508

ROTARY SPADING MACHINE Filed Aug. 5, 1963 7 Sheets-Sheet 2 a comacfcircle b generating circle Fig. 6A

hypofhefic surface over which ihe circle; rolls wii'houf Slip.

F ig.6B

INVENTOR A LEXANDRE HOROW/ 7'Z ATTORNEY5 Nov. 9, 1965 A. HOROWITZ ROTARYSPADING MACHINE 7 Sheets-Sheet 3 Filed Aug. 5, 1963 INVENTOR ALEXA NDREHOROW/ 7'Z ATTORNEY5 Nov. 9, 1965 A. HOROWlTZ 3,216,508

ROTARY SPADING MACHINE Filed Aug. 5, 1963 '7 Sheets-Sheet 4 I I I2111111111 ALEXANDRE' HOROW/TZ ATTORNEYS 7 Sheets-Sheet 5 INVENTORALEXANDRE HOROW/TZ A. HOROWITZ ROTARY SPADING MACHINE Nov. 9, 1965 FiledAug. 5, 1963 ATTORNEYS Nov. 9, 1965 A. HOROWITZ 3,216,508

ROTARY SPADING MACHINE Filed Aug. 5, 1965 7 Sheets-Sheet 6 Fig. 2/

Fig. 20

INVENTOR ALEXANDFE HOROW/T Z lax/Why ATTORNEYS Nov. 9, 1965 A. HOROWITZ3,216,508

ROTARY SPADING MACHINE Filed Aug. 5, 1963 7 Sheets-Sheet 7 INVENTORALEX/ANDRE HOROW/TZ WWW/W ATTORNEY5 United States Patent Ofiice3,216,508 Patented Nov. 9, 1965 3,216,508 ROTARY SPADING MACE AlexandreHorowitz, Eindhoven, Noord Brabant, Netherlands, assignor to N.V.Outwikkelirigmaatschappij Multinor'm, Amersfoort, Netherlands, acorporation of the Kingdom of the Netherlands Filed Aug. 5, 1963, Ser.No. 299,739 14 Claims. (Cl. 17295) The present application is acontinuation-in-part of the copending patent application filed November19, 1954, having the Serial No. 470,086, by the same named inventor andissued on February 4, 1964, as Patent No. 3,120,279.

The present invention relates to a machine for cultivating the soil,more particularly, to a rotary spading machine for simulating the manualspading and turning over of the soil.

It has long been known that from an agricultural point of view spadingof the soil to dig up lumps of earth and turn these lumps over or ontheir sides is the best possible Way of preparing soil for cultivation.However, it is readily apparent that hand spading of the soil isimpractical in cultivating large areas since a considerable amount oflabor and time would be required. I

When preparing soil for cultivation by spading, the lumps of soil shouldbe dug up and then turned over through an angle of at least 90 prior todepositing back on the ground. In this position, the soil will beexposed to the atmosphere and the weeds and other growths in the top ofthe lumps of soil will be buried so that this plant material will bekilled.

The conventional apparatus for preparing the soil for cultivationconsisted of the plowshare which was pulled through the soil in order toplow the soil and turn the soil over. The use of a plowshare has severaldisadvantages which may be listed as follows:

(1) A substantial amount of power is necessary to pull the plowsharethrough the soil.

(2) When slippery soil is being plowed, the tractor which isconventionally used to pull the plowshare will slide over the soil dueto the heavy resistance of the plowshare in moving through the soil.

(3) The plowshare is unable to adequately prepare the soil forcultivation from an agricultural point of view.

This inadequate preparation will be apparent by pointing out that inplowing heavy clay soil long strips of the soil are wholly or partiallyturned. The soil, however, is not broken up into desired lumps of soil.Thus, instead of the desired lumps of soil, one merely has long stripsof soil in the cultivated ground.

Another aspect of inadequately preparing the soil for cultivation isthat the sliding movement of the plowshare on the bottom of the furrowmay clog up the bottom of the furrow so as to hinder the penetration ofthe bottom of the furrow by the roots of the plants. Further, theclogging of the bottom of the furrow will hamper the drainage orabsorption of rain water so that during heavy rainfalls polls of waterwill accumulate upon the plowed field. Prior to plowing of the soil, allof the water falling upon the soil will be absorbed therein so thatthere is 100% penetration of the water in unplowed soil. In contrastthereto, there may be only a 5% penetration of the water in the furrowsof plowed ground when the bottoms of the furrows have been clogged bythe plowshare.

As it became desirable to cultivate larger areas of land attempts weremade to devise apparatus which would replace the conventional handtilling of the soil. Such forms of appartus were essentially structuresattempting to simulate manual spading of the soil. One form of an earlycultivator comprised a drum-like member which had a plurality of curveddigging blades extending outwardly from the periphery thereof. Thisdrum-like cultivator was then pullled over the ground by horses or atractor, and the digging blades purported to dig up and turn over thelumps of soil in a manner similar to that accomplished by hand spadingof the soil. The rolling movement of the drum-like member over theground enabled the substantially involute shaped digging blades topenetrate into the ground and after passing the deepest point ofpenetration to lift out of the ground a lump of earth. The size of thelump of earth depended upon the depth to which the digging bladespenetrated the soil.

When merely dragging the drum-like cultivators over the ground, it wasunexpectedly found that high traction forces were necessary to pullthese cultivators during the plowing operation. These traction forceswere even greater than those required to pull a plowshare through thesoil when soil adhered to the plowshare. These high traction forces weredue to the following:

(1) Friction between the convex surfaces of the digging blades and theundug soil.

(2) The forward component of force exerted against the digging blade bythe soil as the cultivator was pulled over the ground.

The friction between the digging blade and the undug soil occurred asthe digging blade was penetrating into the soil. This friction wassubstantial, particularly when attempting to plow heavy or wet claysoils.

With respect to the forward component of force, it is apparent that bypulling such a drum-like cultivator over the ground the rolling movementof the digging blade Wheel or drum is obtained by means of reactionforces exercised by the ground upon the leading convex surfaces of thedigging blades which are in contact with the undug soil. As thesedigging blades penetrate into the ground, their convex surfaces slidealong the undug soil during the transmission of the pulling or tractionforces to produce a slow rotation of the digging blade drum. It istherefore apparent that a considerable amount of friction must beovercome during the penetrating movements of each digging blade. v I

As a result, these previously devised drum-like cultivators could beused only in light sandy soil. When attempting to plow wet clay, theweight of the cultivators had to be greatly increased so that the bladescould penetrate into the soil. The addition of this weight, however,further increased the traction force necessary to pull the drum-likecultivator and the cultivator tended to compress the soil, thus in turnrendering more difiicult the penetration of the soil by the diggingblades.

It is therefore the principal object of the present invention to providea novel and improved cultivator for tilling the soil. k

It is another object of the present invention to provide a rotaryspading machine which digs up lumps of soil and then deposits the lumpsof soil upon the ground to simulate manual spading of the soil. I

It is a further object of the present invention to provide a rotaryspading wheel with improved structure for pivoting digging blades in apredetermined manner.

It is a further object of the present invention to-provide a rotaryspading machine which can be particularly adapted for the digging ofditches.

The present invention discloses a cultivator which is a considerableimprovement over the drum-like cultivators previously known and solvesthe foregoing agricultural problems. The present cultivator essentiallyincorporates two measures which overcome the disadvantages of the priorart Cultivators. One feature of the present cultivator is the positivedriving of the digging blade wheel and not merely pulling the cultivatorover the ground so that the rotational movement of the digging bladewheel is no longer obtained by means of the reaction forces upon theleading convex surfaces of the blades by the ground. This measure initself considerably reduced the power necessary to move the cultivatorover the ground. The second feature resides in rotatably driving thedigging blade wheel at such a speed relationship so that the rotaryspeed of the digging blade wheel is somewhat greater than wouldcorrespond with the rotary speed obtained when the digging blade wheelnormally rolls over the ground.

The present cultivator essentially comprises a frame having one or moresupporting wheels at one end thereof and at least one supporting memberat another end thereof for controlling the operational depth. A diggingblade wheel having a hub with a plurality of curved digging bladesmounted thereon is rotatably mounted on a shaft carried by the frame. Apower source comprising a motor is drivingly connected through a geartransmission to the digging blade wheel and is also connected to thesupporting wheels of the frame. The gear transmission is constructed soas to drive the digging blade wheel at a particular speed relationshipwith respect to the speed of the frame over the ground surface.

Each of the digging blades is so shaped that a cross section of eachblade in any plane perpendicular to the central axis of the diggingblade wheel comprises an involute generated in the direction of rotationof the digging blade wheel. In addition, any point on the digging bladegenerates a cycloidal movement during the movement of this cultivatoralong the ground surface.

The digging blades may be either fixedly mounted in helicoidal positionson the digging blade wheel, or can be pivotally mounted on the wheel. Amechanism is provided in the hub of the digging blade wheel to pivot thedigging blades through an angle of about 90 after each blade emergesfrom the ground bearing a lump of soil so that pivoting of the bladewill deposit the lump of soil in either the same or in an adjacentfurrow. Helicoidally mounted digging blades will deposit lumps of soilin the adjacent furrow.

Other objects and advantages of the present invention will be apparentupon reference to the acompanying description when taken in conjunctionwith the following drawings, wherein:

FIGURE 1 is a side elevational view of the rotary spading machineaccording to the present invention;

FIGURE 2 is a top plan view of the rotary spading machine illustrated inFIGURE 1;

FIGURES 3 through 5 are diagrams illustrating the cycloidal movement ofthe involute shaped digging blades, with FIGURE 3 representing a priorart cultivator;

FIGURES 6A and 6B are diagrams illustrating vectorially therelationships when the digging blade wheel rotates at different speedswith respect to the ground surface;

FIGURE 7 is an overall perspective view of a helicoidal digging bladewheel structure employed on the rotary spading machine of the presentinvention;

FIGURE 8 is a perspective view of a portion of a helicoidal diggingblade mounted on the wheel structure of FIGURE 7;

' FIGURE 9 is a side elevational view of the concave or digging surfaceof a specially reinforced digging blade for the rotary spading machineof this invention;

FIGURE 10 is a front elevational view of a portion of a digging blade ofFIGURE 9, with the reinforcing strip being shown in section;

FIGURE 11 is a perspective view of a digging blade Wheel of the presentinvention having pivotally mounted digging blades, with a portion of thewheel structure being cut away for purposes of clarity;

FIGURE 12 is a top plan view of another modification of a digging bladewheel provided with pivotally mounted digging blades;

FIGURE 13 is a side elevational view of the digging blade wheel shown inFIGURE 12;

FIGURE 14 is a partial sectional view taken along a plane perpendicularto the rotary axis of the digging blade wheel of FIGURES 12 and 13, andillustrating the mechanism for pivoting the digging blades;

FIGURE 15 is a partial sectional view taken along the rotary axis of adigging blade wheel of FIGURES 12 and 13, and further illustrating thepivoting mechanism shown in FIGURE 14;

FIGURE 16 is a view similar to that of FIGURE 14, and showing amodification of the mechanism for pivoting the digging blades;

FIGURE 17 is a side elevational view of a modification of the rotaryspading machine of this invention;

FIGURE 18 is a top plan view of the modification shown in FIGURE 17;

FIGURE 19 is a side elevational view of the rotary spading machine ofthe present invention in another modification;

FIGURE 20 is a top plan view of the modification shown in FIGURE 19;

FIGURE 21 is a perspective view of a modified digging blade wheelaccording to the present invention, particularly adapted for use as astone picker;

FIGURE 22 is a top plan view of a modified rotary spading machineprovided with braking means;

FIGURE 23 is a side elevational view of a modified digging blade wheelprovided with a deep cutting device;

FIGURE 24 is a top plan view of the modified digging blade wheel ofFIGURE 23; and

FIGURE 25 is a top plan view of a modification of the present inventionparticularly adapted for digging a ditch.

With reference to the drawings wherein like reference numerals indicatethe same parts throughout the various views, a specific embodiment andseveral modifications of the present invention will next be described indetail.

With particular reference to FIGURES 1 and 2, the rotary spading machineof the present invention comprises a frame 1 upon which a digging bladewheel structure 2 is mounted toward the rear thereof, while supportingwheels 3 and 4 are mounted on the frame toward the front thereof.

The construction of the digging blade wheel 2 is shown in greater detailin FIGURES 7 and 8 and comprises a tubular hub 5 which is rotatablymounted upon a shaft 6 which is stationary and mounted on the frame 1.The

hub 5 is provided at both ends with circular flanges 7 and 8.

A plurality of curved digging blades 9 (for example, three, four or six)are mounted helicoidally between the flanges 7 and 8 by means ofprojecting portions 9A and bolts 10, and each blade has an involutesection when viewed axially of the blade wheel 2 with the involute beinggenerated by a base circle coaxial with the wheel structure.

The involute cross section of the digging blades can be achieved duringactual manufacture by fabricating the digging blades from portionshaving circular and straight cross sections.

The diameter of flange 7 is smaller than the diameter of flange 8 sothat the dug-up lumps of earth may easily slide off helically shapeddigging blades. The diameter of flange 8 is approximately equal to thatof the contact circle which will presently be defined in detail.

In order to maintain the bottom of the furrow being formed in a straightline, parallel to the surface of the ground, the digging blade meansshould have such a length that it could be so spaced on the diggingblade wheel that the tips of adjacent digging blades describe cycloidalcurves which overlap each other inside the soil beneath the surface ofthe ground. Thereby a furrow is excavated whose bottom is ofapproximately uniform depth throughout the whole length thereof.

With reference to'FIGURES 9 and 10, one edge of the digging blade 9 isreinforced near its tip in order to resist the'impact of heavy loads andto prevent distortion of the digging blades when penetrating into thesoil.

This reinforcing structure comprises a crescent-shaped strip 27 which isfastened to the edge of the digging blade 9 by a number of bolts 27awhose heads are countersunk so that the tops of the heads will be flushwith the digging blade surface. This reinforcing strip 27 is sharpenedalong its edge 2712 as illustrated in FIGURE 10, which is the cuttingedge for the lateral side of the lump of earth to be dug up. The rear ofthe reinforcing strip 27 is shaped so as to decrease friction with thesoil. The thick portion of the strip indicated at 270, is used forfastening the digging blades 9 to the flange 8 by the bolts 10, asdescribed above.

If desired, the digging blades 9 may be further reinforced by employingspecial supports between the rear surface of the digging blade 9 and theflange 8.

Propulsion of the spading machine on the road with the digging bladewheel 2 in the raised position is obtained through the driving wheel 3alone. The driving wheel 3 is rigidly mounted on a hollow shaft 11 whichis rotatably mounted in the frame 1. A removable shaft 12 is rotatablysupported within the hollow shaft 11 and the supporting wheel 4 ismounted on the shaft 12 with the result that the wheel 4 is freelyrotatable.

A second frame structure 13 is pivotally attached to the hollow shaft 11and carries a freely rotatable rear wheel 14, with a steering handle 15being attached to this second frame 13. The shaft of the rear wheel 14is positioned behind the shaft 6 of the wheel structure 2 when viewed inthe direction of forward movement of the spading machine. The frame 13also carries a pinion 16 to which is attached a hand wheel 17. Thepinion 16 meshes with a rack 18 which is attached to the machine frame 1near the shaft 6. The rear portion of the frame 1, together with thedigging blade wheel 2, can be raised or lowered by rotating the pinion16. A ratchet engageable with the pinion 16 may be employed to lock theframe 1 in a desired working position.

When the digging blade wheel 2 is raised, the spading machine can movefreely since this digging blade wheel does not contact the groundsurface. The freely rotatable supporting wheel 4 will be pulled somewhatlaterally, as indicated by the dashed position as shown in FIGURE 2,because the digging blade wheel 2 is positioned laterally of thelongitudinal center line of the spading machine. The balance of forcescan also be obtained by using two adjustable supporting wheels. Thespading machine can also be kept in equilibrium by the use of acounterweight 19, as shown in FIGURE 2.

The driving wheel 3 is driven by a motor 20 located at the front of thespading machine and mounted on the frame 1. The motor 20 powers thedrive shaft 21 and power is transmitted to a shaft 24 through gears 22and 23. The shaft 24 transmits power to the hollow shaft 11 by a worm 25meshing with suitable gearing on the hollow shaft 11. The driving of thewheel 3 in this manner will determine the forward speed of the spadingmachine.

The digging wheel 2 is driven by the gear 22 through a worm 26 whichmeshes with suitable gearing on the hub of the wheel 2.

In order to obtain the results of the present invention, the diggingblade wheel must be driven at a particular speed relationship withrespect to the speed with which the spading machine is propelled overthe ground surface.

Contrary to the situation with the digging blade wheel 2 in its raisedposition, during which the wheel 3 propels the machine over the roadsurface, the actual propelling of the machine in its operative position(digging blade wheel lowered) is produced by the digging blade wheel,which crawls through the ground. The supporting wheel 3 once againdetermines the forward speed 6 of the spading machine, this time byexerting a braking force on the forward movement of the machine. Thisresult is obtained with the aforementioned particular speedrelationship. This speed relationship can be clearly describedgeometrically by reference to the following terms:

Contact circle.A cross section of the cylindrical surface defined by thepoints on the digging blades which merely contact the surface of theearth without penetrating into the same.

lnvolute circle.A base circle for generating the in volute profile ofthe digging blades on the digging blade wheel structure.

Generating circle-Since the cycloid is generated by a point upon thecircle which rolls along a straight line, it is this circle whichisreferred to when describing the cycloidal movement of the diggingblade Wheel.

This generating circle is a circle which makes a rolling movement over asurface without slipping. Normally when a wheel rolls over a surface,the generating circle corresponds with the outer circumference of thewheel which is in contact with the surface. If, however, the rotation ofthe wheel is somewhat greater than would correspond with the correctrolling (without slipping) over the surface, the radius of thegenerating circle is somewhat reduced so that the wheel in question maybe considered to roll over a hypothetical surface which is positionedcloser to the rotational axis of the wheel than the surface in contactwith the outer circumference of the wheel.

This relationship may be further clarified by reference toFIGURES 6A and613 where FIGURE 6A illustrates the situation wherein the wheel rollswithout slipping over a surface. V represents the forward velocity ofthe vehicle, V represents the velocity of the circumference of the Wheelrelative to the surface, and w repre sents the angular velocity of thewheel.

It is pointed out that the'velocity of the circumference of the wheel atthe lowest point of the wheel is zero which means that there is rollingwithout slipping. Thus the linear speed at this lowest point of thewheel with respect to the surface is zero.

In FIGURE 6B, a situation isshown wherein the angular velocity of thewheel is somewhat greater than would correspond with the correct rolling(with-out slipping) over the surface. It is noted that the velocity ofthe outer circumference of the wheel with respect to the surface at thelowest point of the wheel is no longer zero but has a small negativevalue.

It can be further appreciated that under these circumstances the correctrolling occurs on a hypothetical surface which is at a shorter distancefrom the rotational axis of the wheel dependent upon the increase inangular velocity of the wheel with respect to the situation illustratedin FIGURE 6A.

Therefore, FIGURE 68 illustrates the situation which actually exists inthe rotary spading machine according to the present invention.

In view of this speed relationship, geometrically speaking, the radiusof the generating circle of the cycloid is somewhat smaller than theradius of the contact circle.

With reference to the diagrams of FIGURES 3 through 5, the principles ofthe present invention will be further described in these schematicpresentations of the speed relationship between the digging blade wheeland the forward speed of the spading machine when viewing the diggingblade wheel in a plane perpendicular to its rotary axis.

FIGURE 3 represents the speed relationship resulting when a drum-likecultivator is dragged over the ground according to the prior art. Inthis figure, the generating circle b of the cycloidal movement has thesame radius as the involute circle 0 from which the involute crosssection of the digging blades is generated. Also in this figure, thegenerating circle b has the same radius as the contact circle a-it beingnoted that the radius of this contact circle represents the shortestdistance from the rotary axis of the digging blade wheel to the groundsurface. It is thus seen that in FIGURE 3, the radii of the contactcircle a, the generating circle b, and the involute circle areidentical. The generating circle b is illustrated in eight differentpositions, together with the corresponding positions, adopted by asingle digging blade. Each point on a digging blade follows a cycloidalcurve.

In position I, a typical digging blade just contacts the ground surface.In position VIII, the digging blade has obtained its maximum length ofpenetration into the ground, i.e. since b equals c the digging blade isdeeply buried. The point of the digging blade which is located at thesurface of the soil in each position operates as the pivoting point ofthe shovel during its movement below the surface of the ground. Theactual digging up action of the digging blade occurs only after thedigging blade has reached its greatest depth of penetration into thesoil which corresponds to position V but is not identical with thegreatest length of penetration of the digging blade.

In FIGURE 4 is illustrated the various positions I-VIII of a diggingblade carrying out a cycloidal movement wherein generating circle b hasa smaller radius than the contact circle a. The involute circle 0 of theinvolute has the same radius as the generating circle b.

In FIGURE 5, the generating circle b also has a radius smaller than thecontact circle a. The base circle 0 of the involute, however, has thesame radius as the contact circle a.

In both FIGURES 4 and 5, there occurs a retracting movement of thedigging blade in the soil. This movement provides for thinner slices ofsoil being dug up so that the portions of soil cannot stick betweenadjacent digging blades. This retracting movement also withdraws thecontact surface of the digging blade from the undug soil in front of thedigging blade, thus reducing the friction between the digging blade andthe undug soil.

It has been determined that the speed relation illustrated in FIGURE 5provides the best results with the present spading machine. In thisrelationship the radius of the involute circle c is greater than theradius of the generating circle b and identical with contact circle a.Specifically, these results are attained when the radius of thegenerating circle b is from 100% to 30% of the radius of the contactcircle a. Preferably and for optimum results, the radius of thegenerating circle should be from 80% to 60% of the radius of the contactcircle. It has also been discovered that the radius of the involutecircle should be less than the radius of the contact circle.

' The speed ratios of the various components of the power trains in thespading machine of the present invention are such that when the drivingwheel 3 is rolling on the ground surface, the speed at the bottom of thecontact circle a of the digging blade wheel 2 is small, but in anopposite direction with respect to the forward -movement of the machineover the ground. 7

The following is a specific example through which the aforementionedspeed relationship is obtained.

Speed of motor 20 3000 rev/min. Gear ratio 22 1:5. Gear ratio 23 4:5.Worm ratio 25 1:20. Worm ratio 26 1:20. Diameter of contact circle ofthe shovel-bearing wheel 2 24". Diameter of driving wheel 3 24". Speedof the machine 3 ft./sec.=2 m./h.

To further illustrate the principles of the present invention, thefollowing are the dimensions of a digging blade wheel and circles asdescribed above, similar to 8 the 6-bladed spading machine illustratedin FIGURE 1 of the drawings:

Cm. Outer diameter of digging wheel 105 Diameter of contact circle a 51Diameter of generating circle b 45 Diameter of involute circle c 48Spading depth 27 The above dimensions will give the proper relationshipfor achieving the results of the present invention as described above.The lower limit of the diameter of the generating circle is 17 cm. whichis about 30% of the diameter of the contact circle.

If the diameter of the generating circle falls below the lower limit of30%, then the lumps of earth dug up by the digging blades will be thrownout too far because of the centrifugal force of the rapidly rotatingshovel wheel. This will not produce the result of the present invention, namely to dig up lumps of earth and deposit them in place onthe surface of the ground.

The spading machine of the present invention is operated in thefollowing manner:

During the transfer of the spading machine to the land to be cultivated,the gear 22 is disconnected from worm 26. The frame 1 is raised so thatthe digging blade wheel 2 does not touch the ground. Engine 20 willpropel the driving wheel 3. Whenit is desired to commence the plowing,gear 23 is disconnected from worm 25 and the driving wheels (one orboth) are locked, then gear 22 is shifted into engagement with worm 26and the ratchet of gear 16 is disengaged. Motor 20 now drives only thedigging blade wheel 2. The digging blade wheel 2 will dig into theground until its deepest point of penetration has been reached. Thisdepth of digging is controlled either by bearing flange 8 on one side ofthe wheel, by laterally projecting elements (not shown) attached to thedigging blades, or through a limiting connection between the frame 1 andthe secondary frame 13 After the digging blade wheel has penetrated intothe ground, the driving wheels are released and gear 23 is again engagedwith worm 25. At this point the actual plowing begins. The spadingmachine is steered 'by a handle 15. During the movement of the machinethe dug-up earth is sliding downwardly and laterally off thehelicoidally mounted blades 9 and will to some extent be depositedrearwardly of the machine as the result of centrifugal force. The dug-uplumps of earth are rotated through an angle of about prior to beingdeposited back on the surface of the ground.

The above described embodiment employs digging blade wheels havingdigging blades helicoidally mounted on the wheel structure. The rotaryspading machine of the present invention, however, also employs diggingblades which are not helicoidal in shape, but whose bases are parallelwith the rotary axis of the digging blade wheel. If it is desired todeposit the dug-up lumps of soil laterally into an adjacent furrow ordirectly into the same freshly plowed furrow, the digging blades can beoperated through a mechanism which pivots the blades.

In FIGURE 11 there is illustrated a modified digging blade wheelemploying pivotally mounted digging blades. This digging blade wheelcomprises coaxial cylinders 60 and 61. -Digging blades 63 are mountedonblade shafts 62a which are inserted into the tubular member 62. Thepivoting or tilting mechanism is mounted within the cylinder 60 whichengages the lower end of the digging blade shaft 62a to pivot thedigging blades in a predetermined manner.

Under certain circumstances, it is desirable to position the tubularmembers 62 so that they cross over the main shaft 5 of the digging bladewheel and are not positioned radially to this shaft. As a result, thedigging blade shafts remain in one or more planes perpendicular to themain shaft 5 but the axes of the blade shafts do not intersect thecentral axis of the main shaft 5.

The digging blade shafts can be fastened either to the center or toeither side of the digging blades. Both arrangements will facilitate thedepositing of lumps of soil directly into the freshly plowed furrow.Pivoting mechanism operates to pivot the digging blades at the rightmoment to accomplish this deposition of the lumps of soil. In thedigging position, the blade has its surface substantially parallel tothe central axis of the wheel structure and the blade is pivoted about90 after lifting a lump of soil to deposit this lump on its side.

A further modification having pivotable digging blades is illustrated inFIGURES 12 through 16. This modification of the digging blade wheel isparticularly adapted for use on a rotary spading machine attached to atractor and driven by the tractor power take-off shaft. The wheel has aplurality of adjacent digging blade wheels with each wheel comprisingfour pivotally mounted digging blades.

This spading machine is mounted on the conventional 3-point hitch foundon agricultural tractors. Changing of the gear ratio of the tractor willchange the speed of the digging blade wheel and hence vary thegenerating circle. Generally, the contact circle will remain constant.

The digging blades are pivotally mounted on the rotary spading machinewith a cam mechanism being provided to pivot the digging blades in apredetermined manner. The digging blades similarly have involutecross-sections and are mounted on the end of curved supporting armswhich in turn are pivotally mounted on the hub of the spading machine.During the actual penetration of the digging blades into the soil, thesurface of the digging blade is parallel to the rotary axis of thedigging blade wheel. After the digging blade emerges from the soilbearing a lump of earth, the blade is then tilted to an angle of about90 to dump the lump of soil in the same or in an adjacent furrow.

Each digging blade 9 is fixed upon a curved supporting arm 90 with saidarms being rotatably mounted on a casing 91. The casing 91 is mountedaround a cylindrical hub 92 which is coaxial with the main shaft 5. Amechanism for pivoting the blades 9 according to a predetermined manneris enclosed in the casing 91. As can be seen from FIGURE 12, the diggingblade may be mounted at its center line to the supporting arm 90 (fulllines), or at one side of the center line.

The adjacent casings 91 are angularly displaced with respect to eachother. This produces a more uniform load on the engine as the diggingblades penetrate into the soil at different times. Further, itfacilitates the pivoting movement of the blades as the displacement ofone blade is not hindered by a blade in an adjacent set of blades.

A mechanism for pivoting the digging blades of FIG- URES l2 and 13 isillustrated in FIGURES l4 and 15 and will be described in detail. Eachcurved support arm 90 is fixed to a shaft or stub axle 93 mountedinbores 94 and 95 of the casing 91 in such a manner that the variousshafts 93 extend in a plane substantially perpendicular to the mainshaft of the digging bladewheel. A portion of each of the shafts 93between the bearings 94 and 95 has been flattened on opposite sides.Through a hole in this flattened portion a bolt 96 supports a followerarm 97 in a position perpendicular to the shaft 93 in a direction towardthe axis of the main shaft 5. A roller 98 which is essentially a camfollower, is rotatably mounted on the end of the arm 97. A- cylindricalcam block 99 is fixedly mounted coaxially on the shaft 5. The cam blockis provided with a curved cam groove 100 around its circumference. Amajor portion of the groove is such that the rollers 98 are kept in aposition as indicated in the upper portion of FIGURE 15. The diggingblades 9 are then in the digging position.

In a further portion of the cam groove the curvature changes so thatafter about a 45 rotation of the digging blade wheel, the shaft 93 isrotated through an angle of at least 90. The digging blades 9 are thenin what might be called the delivery or deposit position for dumping thelumps of soil. In the lower portion of FIGURE 15, the shaft 93 isillustrated as being midway between these two above-mentioned positions.The pivotingmov'ement of the digging blade begins when the'digging'blade is in the position indicated at VIII in FIGURES. However,this moment can be delayed if required. In the last portion of the camgroove 100 the roller 98 is returned to its position as indicated in theupper portion of FIGURE 15. The digging blade willthen again'be broughtin its digging position.

In this modification as illustrated in FIGURES 12-15, each set ofdigging blades has its own cam block for guiding the pivoting movementof the digging blades.

Proceeding next to FIGURE 16, there is'show'n'a-modified pivotingmechanism utilizing a longer moment arm between the stub axle of thedigging blade and'the cam follower. This reduces the forces exerted onthe mechanism without the necessity for enlarging the outer dimensionsof the hub of the digging blade wheel. In this modification the camfollower engages the cam profile over an arc distance of at least 45and'prefe'rably from that area of the 'cam groove which is nearest tothe stub axle upon which that particular follower arm is mounted.

A portion of one digging blade wheel is shown in FIGURE 16 and isillustrated at200'. This'unit comprises a central stationary shaft 201'having a cam block 202 fixedly mounted thereon, with'a cam groove 203being provided in the circumference 'of the 'cam block. The cam block isenclosed by a'rotatable tubular hub 204, the rotary axis of whichcoincides with the central axis of the shaft 201. Tangentially supportedin bearings 205 and-206 along the outer circumfer'ence of the hub 204,are three stub axles 207. Secure'd'to the end 208 of the stub axle is adiggingblade (not shown) which has an involute cross section asdescribed previously.

Mounted on each stub axle 207 is a curved follower arm 209 extending inthe annular space between the outer circumference of the cam block 202and the inner circumference of the hub 204. On'the inner end of thefollower arm 209' is mounted a shaft 210 upon which is rotatably mounteda roller 211 which functions as a cam follower and is engageable withthe' cam groove 203.'

As-is clearly apparent from FIGURE 16, the cam follower 211 engages thecam groove 203 over are distance of about 90 from that area ofthecam'groove which is nearest to the stub'axle 207; Accordingly, asufficiently long lever arm is obtained, as indicated at A, for pivotingthe stub axle 207 and the digging blade mounted thereon. Accordingly,the forces ex'ertec l between the cam follower 211 and the cam'block202*are considerably reduced and remain well underthe maximum limitswhereby the operatinglife of thepivoting mechanism is considerablylengthened? Because of'the position of the cam' follower'211 Withrespect to the stub axle 207, a rather large movement willhave to beimparted to this cam' follower by the cam profile 203 in order toachieve a pivotin'g of the digging blade through an angle of atlea'st'90.

Where the rotary spading machine comprises a plurality of such spadingunits, positioned adjacent each other, no difiiculties are experiencedas in an axial direction with respect to the central shaft 201sufiicient space is provided for each spading unit.

FIGURES 17 and 18 show a rotary spading machine frame 1 and a diggingblade wheel 2 with a front supporting wheel 30 and an upwardly anddownwardly displaceable rear supporting wheel 31. The'digging bladewheel 2 can be raised or lowered into the soil with the aid of the wheel31. The wheel '30' and the digging blade wheel 2 are driven in the samemanner as in the embodiment illustrated in FIGURES 1 and 2.

A multi-unit spading machine is shown in FIGURES blades are mirrorimages of each other.

19 and 20. The frame 1 carries three digging blade wheels 50, 51 and 52mounted in corresponding bearings and driven by chains 50a, 51a and 52a.Through the staggered position of the digging blade wheels a compact andspace saving construction is obtained which enables a wider tract ofground to be spaded. Digging blade wheel 52 in the rearward portiondeposits dug up soil in the furrow of wheel 51 and this in turn depositsits dug up soil in the furrow of wheel 50. The frame 1 is provided atboth ends with supporting wheels 53 which may raise or lower the body soas to vary the height of the digging blade wheels above the groundsimilar to the modification illustrated in FIGURES 17 and 18. The seatfor the operator of the machine may be provided on top of the plow.

Proceeding next to FIGURE 21 there is shown a further modification ofthe present invention which is particularly adapted for picking up thestones from a field or digging up potatoes or other tuberous plants. Inthis modification the digging blades are so positioned on the wheel thatthe surfaces are parallel to the rotary axis of the digging blade wheel.As a result dirt dug up by these blades is transported into the interiorof the wheel. From the interior of the wheel the soil can be ejectedlaterally of the wheel or handled in any other desired .way.Accordingly, the soil may be sieved inside the wheel whereupon the soilis returned to the ground after having passed through the sieve. Stones,however, will be laterally discharged therefrom.

In this modification a digging blade wheel comprises a flange 71attached to a hub 70, with the flange 71 .carrying a plurality ofdigging blades 72, with each blade having a plurality of tines thereon.These fork-like digging blades are attached to a ring 73. Abasket-shaped sieve 75 is suspended from the hub 70 and remains in thecorrect position by gravity. The dug-up soil descends into the sieve.Because of the tilted position of the sieve, the stones or the like willroll laterally out of the wheel through opening 74 and may be easilygathered. The speed of rotation of this wheel should be so low as toprevent discharge of the dug-up soil by centrifugal force. The width ofthis wheel can be substantially greater than the width of a shovelbearing wheel having helicoidally shaped blades.

In FIGURE 22 there is illustrated a rotary spading machine having asingle digging blade wheel 2 driven by the motor 20. In order to slowdown the forward movement of the machine resulting from the rotation ofthe shovel bearing wheel, the spading machine drags a harrow 28 orimilar agricultural implement which has a braking effect. At the sametime, the surface of the soil is graded or leveled.

FIGURES 23 and 24 illustrate a digging blade wheel .81 to which is addeda star-shaped wheel of sheet metal 80 attached coaxial on the side ofthe digging blade wheel. This star wheel functions as a deep cutter forcutting up any impermeable layer of the sub-soil. In FIGURE 23 a topsoil is indicated at 82, and the impermeable layer of the sub-soil whichis penetrated by the star wheel is indicated at 83.

Proceeding next to FIGURE 25, there is shown a modification of therotary spading machine of the present invention which is particularlyadapted for digging a ditch.

.This modification essentially comprises an arrangement of a pair 'ofsimilar digging wheels 2 positioned adjacent each other and coaxially,but with the digging blades being inverted symmetrically with respect tothe vertical central plane of the spading machine. As'a result, thedigging The arrangement of digging wheels is pulled by a tractor 29. Thewheels are driven through a transmission enclosed in the housing 2a andpowered through a conventional power take-off shaft of the tractor. Thedigging blades 9 may be of the helicoidal type or of the pivoting type.Thus the digging action of these two digging blade Wheels will dig uplumps of dirt and throw the lumps of the dirt to the side of the furrowwhich is dug. The result Will be a clean ditch having a widthsubstantially equal to the combined width of the two digging bladewheels.

If the digging blade wheels are provided with helicoidally mounteddigging blades, it is necessary to have the tip of the blade whichpenetrates the soil positioned at that side of the digging blade WheelWhich faces rearwardly with respect to the direction of movement of therotary spading machine. As a result, a furrow of maximum width is dug byoverlapping the work of two adjacent digging blade wheels.

Thus, it can be seen that the present invention discloses a rotaryspading machine which closely simulates a manual grading of the soil.The spading machine may be provided with fixedly mounted helicoidallyshaped digging blades or with pivotally mounted digging blades which canbe pivoted in a predetermined manner by mechanisms supported in the hubof the digging blade wheel. The rotary spading machine may be furthermodified as described above, to accomplish several importantagricultural tasks.

It will be understood that this invention is susceptible to modificationin order to adapt it to different usages and conditions and,accordingly, it is desired to comprehend such modifications within thisinvention as may fall within the scope of the appended claims.

What is claimed is:

1. A rotary spading machine comprising a frame supported for movementover the ground surface, a wheel structure mounted for rotation on saidframe, a plurality of digging blades mounted on said Wheel structure forrotation therewith and curving outwardly therefrom in the direction ofrotation thereof, a portion of each blade when viewed axially of thewheel structure defining an involute generated by a base circle coaxialwith the axis of rotation of said wheel structure, driving means forrotating said wheel structure in the direction corresponding to thedirection of movement of the machine over the ground surface at such aspeed that the generating circle of the cycloidal movement of saiddigging blades has a radius of 90% to 30% of the radius of the contactcircle formed by the cross section of a cylindrical surface contactingthose points on said blades which contact the ground surface withoutpenetrating the same, the base circle of said involute having a diametergreater than the diameter of said generating circle and smaller than thediameter of said contact circle.

2. A rotary spading machine as claimed in claim 1, wherein said diggingblades are mounted helicoidally on said wheel structure, the leadingedge of one blade coinciding with the trailing edge of the next adjacentblade when viewed in an axial direction.

3. A rotary spading machine as claimed in claim 1, wherein said diggingblades are so spaced around said wheel structure that each blade willstart penetrating into the soil when the preceding blade has completelyentered into the soil.

4. A rotary spading machine as claimed in claim 1, wherein thegenerating circle of the cycloidal movement of said digging blades has aradius of from to 60% of the radius of the contact circle formed by thecross section of a cylindrical surface contacting those points on saidblades which contact the ground surface without penetrating the same.

5. A rotary spading machine comprising a frame supported for movementover the ground surface, means for propelling said frame over saidground surface, a wheel structure mounted for rotation on said frame, aplurality of digging blades mounted on said wheel structure for rotationtherewith and curving outwardly therefrom in the direction of rotationthereof, a portion of each blade when viewed axially of the wheelstructure defining an involute generated by a base circle coaxial withthe axis of rotation of said wheel structure, driving means for rotatingsaid wheel structure in the direction corresponding to the direction ofmovement of the machine over the ground surface at such a speed that thegenerating circle of the cycloidal movement of said digging blades has aradius of 90% to 30% of the radius of the contact circle formed by thecross section of a cylindrical surface contacting those points on saidblades which contact the ground surface without penetrating the same,the base circle of said involute having a diameter greater than thediameter of said generating circle and smaller than the diameter of saidcontact circle.

6. A rotary spading machine comprising a frame supported for movementover the ground surface, a wheel structure mounted for rotation on saidframe, a plurality of digging blades mounted on said wheel structure forrotation therewith and curving outwardly therefrom in the direction ofrotation thereof, a portion of each blade when viewed axially of thewheel structure defining an involute generated by a base circle coaxialwith the axis of rotation of said wheel structure, digging blades beingso spaced on said wheel structure that the tips of two adjacent diggingblades describe cycloidal curves overlapping each other below thesurface of the soil, driving means for rotating said wheel structure inthe direction corresponding to the direction of movement of the machineover the ground surface at such a speed that the generating circle ofthe cycloidal movement of said digging blades has a radius of 90% to 30%of the radius of the contact circle formed by the cross section of acylindrical surface contacting those points on said blades which contactthe ground surface without penetrating the same, the base circle of saidinvolute having a diameter greater than the diameter of said generatingcircle and smaller than the diameter of said contact circle.

7. A rotary spading machine comprising a frame supported for movementover the ground surface, a wheel structure mounted for rotation on saidframe, a plurality of digging blades pivotally mounted on said wheelstructure for rotation therewith and curving outwardly therefrom in thedirection of rotation thereof, said digging blades being pivotable overan angle of at least 90, a portion of each blade when viewed axially ofthe wheel structure defining an involute generated by a base circlecoaxial with the axis of rotation of said wheel structure, driving meansfor rotating said wheel structure in the direction corresponding to thedirection of movement of the machine over the ground surface at such aspeed that the generating circle of the cycloidal movement of saiddigging blades has a radius of 90% to 30% of the radius of the contactcircle formed by the cross section of a cylindrical surface contactingthose points on said blades which contact the ground surface withoutpenetrating the same, the base circle of said involute having a diametergreater than the diameter of said generating circle and smaller than thediameter of said contact circle.

8. A rotary spading machine comprising a frame supported for movementover the ground surface and having a stationary shaft thereon, a wheelstructure having a tubular hub mounted for rotation on said stationaryshaft, a plurality of digging blades mounted on said wheel structure forrotation therewith and curving outwardly therefrom in the direction ofrotation thereof, a portion of each blade when viewed axially of thewheel structure defining an involute generated by a base circle coaxialwith the axis of rotation of said wheel structure, said digging bladeseach having a stub axle with said stub axles being pivotally mounted onsaid hub tangentially with respect thereto, a cam follower mounted oneach of said stub axles and extending into said hub, a cam fixedlymounted on said stationary shaft, said cam having a groove with sidesurfaces, said cam side surfaces being engageable by said cam followerto swing said cam follower through a 90 arc, said are being in a planetransverse to and symmetrical to a plane including the axis of therespective stub axle and perpendicular to the axis of the shaft, saidcam follower pivoting said digging blades through an angle of about in,a predetermined manner as said wheel structure rotates on said shaft,driving means for rotating said wheel structure in the directioncorresponding to the direction of movement of the machine over theground surface at such a speed that the generating circle of thecycloidal movement of said digging blades has a radius of 90% to 30% ofthe radius of the contact circle formed by the cross section of acylindrical surface contacting those points on said blades which contactthe ground surface without penetrating the same, a base circle of saidinvolute having a diameter greater than the diameter of said generatingcircle.

9. A rotary spading machine comprising a movable frame having astationary shaft thereon, a Wheel structure having a tubular hubrotatably supported on said stationary shaft, said wheel structureincluding a plurality of digging blades each having a stub axle withsaid st-ub axles being pivotally mounted on said hub tangentially withrespect thereto, a cam follower mounted on each of said stub axles andextending into said hub, and a cam fixedly mounted on said stationaryshaft, said cam having a groove with side surfaces, said cam sidesurfaces being engageable by said cam followers to swing said camfollower through a 90 are, said are being in a plane transverse to andsymmetrical to a plane including the axis of the respective stub axleand perpendicular to the axis of the shaft, said cam follower pivotingsaid digging blades in a predetermined manner as said wheel structurerotates on said shaft.

10. A rotary spading machine comprising a movable frame having astationary shaft thereon, a wheel structure having a tubular hubrotatably supported on said stationary shaft, said wheel structureincluding a plurality of digging blades each having a stub axle withsaid stub axles being pivotably mounted on said hub tangentially withrespect thereto, a cam follower arm mounted on each of said stub axlesand extending radially into said hub and having a cam follower mountedon the inner end thereof, and a cam fixedly mounted on said stationaryshaft and having a channel-shaped cam surface engageable by said camfollower to swing said cam follower through a 90 arc, said are being ina plane transverse to and symmetrical to a plane including the axis ofthe respective stub axle and perpendicular to the axis of the shaft,said cam follower pivoting said digging blades in a predetermined manneras said wheel structure rotates on said shaft.

11. A rotary spading machine comprising a movable frame having astationary shaft thereon, a wheel structure having a tubular hubrotatably supported on said stationary shaft, said wheel structureincluding a plurality of digging blades each having a stub axle withsaid stub axles being pivotably mounted on said hub tangentially withrespect thereof, a cam fixedly mounted on said stationary shaft andhaving a cam surface thereon, the tangential positions of saidstub-axles being adjacent the periphery of the cam, and a cam followermounted on each stub axle and engageable with said cam surface at an arcdistance extending circumferentially about 45 90 from that area of thecam surface which is closest to that stub axle to which the respectivefollower is mounted whereby said digging blades are pivoted in apredetermined manner during the rotation of said wheel structure on saidshaft.

12. A rotary spading machine comprising a movable frame having astationary shaft thereon, a wheel structure having a tubular hubrotatably supported on said stationary shaft, said wheel structureincluding a plurality of digging blades each having a stub axle withsaid stub axles being pivotally mounted on said hub tangentially withrespect thereof, a cam fixedly mounted on said stationary shaft andhaving a cam surface thereon, the tangential positions of said stubaxles being adjacent the periphery of the cam, a cam follower armmounted on each stub axle and extending into theannular space betweensaid hub and said cam, the inner ends of said cam follower arms beingpositioned between the stationary shaft and the next adjacent stub axle,and a cam follower on the inner end of each follower arm and engageablewith said cam surface at an arc distance extending circumferentiallyabout 90 from that area from said cam surface which is closest to thestub axle on which the respective follower arm is mounted whereby saiddigging blades are pivoted in a predetermined manner during the rotationof said wheel structure on said shaft.

13. A rotary spading machine particularly adapted for digging ditches,and comprising a frame supported for movement over the ground surface, apair of coaxial wheel structures mounted on said frame for rotation inthe same direction, a plurality of digging blades helicoidally mountedon both of said wheel structures for rotation therewith and curvingupwardly therefrom in the direction of rotation thereof, a portion ofeach blade when viewed axially of its respective wheel structuredefining an involute generated by a base circle coaxial with the axis ofrotation of said wheel structure, said digging blades on one wheelstructure being positioned invertedly symmetrical to the digging bladeson the other wheel structure so that said digging blades are mirrorimages relative to a plane between said wheel structures in thedirection of movement of the machine, driving means for rotating both ofsaid wheel structures in the direction corresponding to the direction ofmovement of the machine over the ground surface at such a speed that thegenerating circle of the cycloidal movement of said digging blades hasaradius of 90% to 30% of the radius of the contact circle formed by thecross section of the cylindrical surface contacting those points on saidblades which contact the ground surface without penetrating the same,the base circle of said involute having a diameter greater than thediameter of said generating circle, the reverse positions of the diggingblades on one wheel structure with respect to the digging blades of theother wheel structure discharging lumps of soil laterally outwardly fromsaid pair of wheel structures.

14. A rotary spading machine particularlyadapted for digging ditches,and comprising a frame supported for movement over the ground surface, apair of coaxial wheel structures mounted on said frame for rotation inthe same direction, a plurality of digging blades pivotally mounted onboth of said wheel structures for rotation therewith and curvingupwardly therefrom in the direction of rotation thereof, a portion ofeach blade when viewed axially of its respective wheel structuredefining an involute generated by a base circle coaxial with the axis ofrotation of said wheel structure, said digging blades on one wheelstructure being positioned invertedly symmetrical to the digging bladeson the other wheel structure so that said digging blades are mirrorimages relative to a plane between said wheel structures in thedirection of movement of the machine, driving means for rotating both ofsaid wheel structures in the direction corresponding to the direction ofmovement of the machine over the ground surface at such a speed that thegenerating circle of the cycloidal movement of said digging blades has aradius of to 30% of the radius of the contact circle formed by the crosssection of the cylindrical surface contacting those points on saidblades which contact the ground surface without penetrating the same,the base circle of said involute having a diameter greater than thediameter of said generating circle, the reverse positions of the diggingblades on one Wheel structure with respect to the digging blades of theother wheel structure discharging lumps of soil laterally outwardly fromsaid pair of wheel structures.

References Cited by the Examiner UNITED STATES PATENTS 93,494 8/69Stevens 17271 101,710 4/70 Chenoweth l72546 704,857 7/02 Castelin l725561,878,442 9/ 32 Hamshaw 172-43 2,342,032 2/44 Bagan l72532 3,012,61612/6 1 Horowitz l7294 3,120,279 2/ 64 Horowitz l72546 X FOREIGN PATENTS71,108 2/ 16 Austria.

965,868 2/50 France.

717, 174 2/ 42 Germany.

927,820 6/63 Great Britain.

ABRAHAM G. STONE, Primary Examiner.

1. A ROTARY SPADING MACHINE COMPRISING A FRAME SUPPORTED FOR MOVEMENTOVER THE GROUND SURFACE, A WHEEL STRUCTURE MOUNTED FOR ROTATION ON SAIDFRAME, A PLURALITY OF DIGGING BLADES MOUNTED ON SAID WHEEL STRUCTURE FORROTATION THEREWITH AND CURVING OUTWARDLY THEREFROM IN THE DIRECTION OFROTATION THEREOF, A PORTION OF EACH BLADE WHEN VIEWED AXIALLY OF THEWHEEL STRUCTURE DEFINING AN INVOLUTE GENERATED BY A BASE CIRCLE COAXIALWITH THE AXIS OF ROTATION OF SAID WHEEL STRUCTURE, DRIVING MEANS FORROTATING SAID WHEEL STRUCTURE IN THE DIRECTION CORRESPONDING TO THEDIRECTION OF MOVEMENT OF THE MACHINE OVER THE GROUND SURFACE AT SUCH ASPEED THAT THE GENERATING CIRCLE OF THE CYCLOIDAL MOVEMENT OF SAIDDIGGING BLADES HAS A RADIUS OF 90% TO 30% OF THE RADIUS OF THE CONTACTCIRCLE FORMED BY THE CROSS SECTION OF A CYLINDRICAL SURFACE CONTACTINGTHOSE POINTS ON SAID BLADES WHICH CONTACT THE GROUND SURFACE WITHOUTPENETRATING THE SAME, THE BASE CIRCLE OF SAID INVOLUTE HAVING A DIAMETERGREATER THAN THE DIAMETER OF SAID GENERATING CIRCLE AND SMALLER THAN THEDIAMETER OF SAID CONTACT CIRCLE.